Didn't they do the dyno on an AWD dyno with a RWD car, or something like that. If I am remembering that correctly that could be a reason for the difference.

Yes alot of the dynos used today are AWD. They are setup to do both RWD and AWD. They used a correction factor but it still came in way below.. Not to mention driving it against the S8 also helped prove how over rated it is.